unsash

verb3

1. •
   To untie the sash that holds an article of clothing.

   • But though she felt curious about the toys Ron had phoned to tell her he was bringing, she wished she could open the front door to Dirk and unsash her robe for him. — 2011
2. •
   To remove or release a sash from.

   • First, close the doors, unsash the curtains, turn off all the lights but the glass lamp. — 2001
3. •
   To open a sash.